Installation manual
Series C Controller Configuration and Operation Manual
7-6 Athena Controls, Inc. 900M050U00
7.4.2 Specifying the Cycle Time for PID Control
When an output is used for PID control, you must specify a cycle time that is appropriate
for your application and the output hardware (see below). The cycle time enables you to
use a discrete output device, such as a solid state relay, to achieve PID control.
For example, suppose the cycle time is set to 10 seconds and the control algorithm
calculates that the output percentage should be 50%. A normally open relay will be
closed for 5 seconds and open for 5 seconds in each ten second cycle. If the output
percentage changes to 70%, the relay will be closed for 7 seconds and open for 3
seconds in each ten second cycle.
The cycle time parameter must be configured, even if the controller is equipped with
analog outputs. In the case of analog outputs, the cycle time entered must be 0.2
seconds. This will have the effect of producing the correctly proportioned analog output
signal.
The output hardware is specified when the controller is ordered. The location of the
output characters in the model number is shown in the installation manual supplied with
the controller. The controller’s model number is on its label.
Model Number Output
Hardware Character
Valid Cycle Times
in Seconds
B 15 to 120
E 0.2 (See Note 1 below.)
F 0.2 (See Note 1 below.)
G 0.2 (See Note 1 below.)
S 0.2 (See Note 1 below.)
T 15 to 120 (See Note 2 below.)
V 0.2 (See Note 1 below.)
X 0.2 (See Note 1 below.)
Y 15 to 120
Note 1: The cycle time for analog outputs must to set to 0.2 for the controller to
drive the analog output properly.
Note 2: “T” outputs directly driving non-inductive loads (small heaters) can have
cycle times as low as 0.2 seconds.
Parameter Name
: Output 1 Cycle Time 1 (A2) and Output 2 Cycle Time (B3)
Name as Displayed:
O1.Cy O1.Cy and O2.Cy O2.Cy
Used By:
all controllers
When Displayed:
if output type is PID
Range:
see table above
Default:
5 seconds
Description:
Used to specify the period of time in which the output completes
an on-off cycle.